Effect of salinisation due to global warming on dengue transmission by mosquitoes

Global climate change is expected to increase the transmission of mosquito vector-borne diseases including dengue in many parts of the world. Environmental temperature influences the development of mosquitoes and the pathogens they transmit. Another environmental concern associated with global warming is the rise in sea-levels resulting in salinization, which may act synergistically with global warming to increase the transmission of mosquito-borne diseases. In previous experiments, the Noble group has shown that Aedes aegypti mosquitoes that may transmit dengue adapt to areas with brackish water. Transcriptome data showed that genes associated with heat shock proteins are highly expressed in brackish water adapted Ae. aegypti indicating that brackish water adaption may indirectly favour thermal tolerance. The effect of adaptation to brackish water habitats on thermal tolerance and vector competence and therefore disease transmission has not been studied and is the focus of our scientific exchange.We aim to determine the vector competence and thermal tolerance of fresh- and brackish-water adapted Ae. aegypti. Because adaptation normally comes with a cost, we expect the vector competence of the adapted lines to change. To test this, we will infect the two Ae. aegypti lines from Sri Lanka with dengue virus in the BSL3 laboratory in Zürich and determine their ability to transmit the virus after 7 and 14 days. In addition, we will test the thermal tolerance of the two lines by growing larvae of the two lines at different temperatures and in water with different salinity. Standard fitness parameters will be measured, and the expression of heat shock proteins determined.The visit of Prof. Noble to Zürich will therefore result in fundamental knowledge that may be used for follow up projects to understand the mechanisms behind the changes in vector competence. In addition, it will allow Prof. Noble to acquire the knowledge and skills work on vector competence in a BSL3 laboratory. The group of Prof. Verhulst will benefit from the collaboration as they have been working on temperature effects on mosquitoes but have no experience with the expression of heat shock proteins or salinisation. There is currently no information on the (synergetic) effect of salt and temperature on Ae. aegypti development and vector competence. Because salinisation becomes more important during global warming the first results obtained during the proposed visit will form the basis for follow up projects and future collaborations between the two groups.